再学 GDI+[10]: DrawClosedCurve - 绘制闭合曲线

本例效果图:

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代码文件:

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unit Unit1;



interface



uses

  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

  Dialogs, StdCtrls, ComCtrls;



type

  TForm1 = class(TForm)

    Button1: TButton;

    TrackBar1: TTrackBar;

    procedure FormMouseUp(Sender: TObject; Button: TMouseButton;

      Shift: TShiftState; X, Y: Integer);

    procedure FormPaint(Sender: TObject);

    procedure FormCreate(Sender: TObject);

    procedure Button1Click(Sender: TObject);

    procedure TrackBar1Change(Sender: TObject);

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



uses GDIPOBJ, GDIPAPI;



var

  PtArr: array of TGPPoint;

  i: Integer = 0;

  tension: Single;



procedure TForm1.FormCreate(Sender: TObject);

begin

  Button1.Caption := '擦除';

  TrackBar1.ShowSelRange := False;

  TrackBar1.Min := -25;

  TrackBar1.Max := 35;

  TrackBar1.Position := 5;

end;



procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;

  Shift: TShiftState; X, Y: Integer);

begin

  Inc(i);

  SetLength(PtArr, i);

  PtArr[i-1].X := X;

  PtArr[i-1].Y := Y;

  Text := IntToStr(i);

  Repaint;

end;



procedure TForm1.FormPaint(Sender: TObject);

var

  g: TGPGraphics;

  p: TGPPen;

  i: Integer;

begin

  g := TGPGraphics.Create(Canvas.Handle);

  p := TGPPen.Create(aclRed, 2);

  g.Clear(aclWhite);



  {最后一个参数是可选的, 默认值是 0.5, 为 0 时曲线会转为直线段}

  g.DrawClosedCurve(p, PGPPoint(PtArr), Length(PtArr), tension);



  p.SetWidth(1);

  p.SetColor(aclBlack);

  for i := 0 to Length(PtArr) - 1 do

    g.DrawEllipse(p, PtArr[i].X-2, PtArr[i].Y-2, 4, 4);



  g.Free;

  p.Free;

end;



procedure TForm1.TrackBar1Change(Sender: TObject);

begin

  tension := TrackBar1.Position / 10;

  Repaint;

end;



procedure TForm1.Button1Click(Sender: TObject);

begin

  i := 0;

  SetLength(PtArr, i);

  Repaint;

  Text := IntToStr(i);

end;



end.


 
   

窗体文件:

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object Form1: TForm1

  Left = 0

  Top = 0

  Caption = 'Form1'

  ClientHeight = 188

  ClientWidth = 264

  Color = clBtnFace

  Font.Charset = DEFAULT_CHARSET

  Font.Color = clWindowText

  Font.Height = -11

  Font.Name = 'Tahoma'

  Font.Style = []

  OldCreateOrder = False

  Position = poDesktopCenter

  OnCreate = FormCreate

  OnMouseUp = FormMouseUp

  OnPaint = FormPaint

  PixelsPerInch = 96

  TextHeight = 13

  object Button1: TButton

    Left = 181

    Top = 155

    Width = 75

    Height = 25

    Caption = 'Button1'

    TabOrder = 0

    OnClick = Button1Click

  end

  object TrackBar1: TTrackBar

    Left = 8

    Top = 155

    Width = 167

    Height = 25

    TabOrder = 1

    OnChange = TrackBar1Change

  end

end